Digital8
Digital8 (or D8) is a digital videotape format invented by Sony in the late 1990s.
Digital8 is the combination of the venerable Hi8 tape-transport with the DV codec. Digital8 recorders use video cassettes identical to those used with the analog Hi8 format, but store audio and video information in digital form (using the industry standard DV codec). Another difference is that the tape is running at a higher speed: where the same tape will record 120 minutes of analog Hi8 NTSC video or 90 minutes of analog Hi8 PAL video, it will only record 60 minutes of Digital8 PAL/NTSC video. Many Digital8 decks does support Long Play though.
The Digital8 format is completely digital and as such, offers superior image quality when compared to the previous formats VHS, Video8 and Hi8. Little or no equipment has been produced for the professional market, although there are no technical barriers opposing its development.
MiniDV/DVC vs. Digital8
The Digital8 format, although physically incompatible, is completely interchangeable with the DVC (Digital Video Cassette, eg. MiniDV) on a data level. Contrary to popular misconception, Digital8 is identical in picture and sound quality to MiniDV. No conversion is taking place when copying footage from Digital8 to DVC or vice versa, the bits stay unchanged.
Market segment
While analog Hi8 video was used by professional electronic news organizations and current affairs TV programs (as well as for amateur use ofcourse), Digital8 remains strictly a format aimed at amateurs. This is likely a reflection of the design goals of the Digital8 format: that is, to serve as a low-cost upgrade path for current customers (from analog Video8 and Hi8), and by leveraging the existing manufacturing infrastructure of 8 mm video equipment.
As of 2005, Digital8 product lines are limited to entry-level consumer gear: state-of-the-art camcorders are constructed with MiniDV tape recorders (this is because MiniDV is the industry standard in this segment, not because Digital8 is in any way inferior in itself). Sony, the formats sole backer, is the only company to produce Digital8 equipment.
Analog recordings
Some Digital8 camcorders offer limited backward compatibility with Hi8 and Video8 analog-recordings. These units can play (but not record) the analog recordings (although only the analog sound recorded on tape -- it's unable to play back digital PCM sound recorded to Hi8 tape by professional equipment), simultaneously performing some rather impressive signal processing (to improve the picture quality) while transcoding the footage into the DV format. This allows analog Video8/Hi8 recordings to be transferred to home computer using the camcorder's Firewire interface in considerably higher quality than normally achieved by ordinary analog equipment.
This feature seems to be gradually phased out of newer Digital8 camcorder designs, at least the cheaper ones. Another possible reason behind it is that Sony is segmenting the market in order to make you pay more for the digitization feature.